Matthew McConaughey has revealed he broke his diet with a carefully constructed cheeseburger after wrapping filming Dallas Buyers Club.

Speaking after scooping the Best Actor in a Drama gong at the SAG Awards on Saturday night, the Texan actor recalled how he indulged in the feast after losing 40lbs to play AIDS campaigner Ron Woodroof.

The Golden Globe winner lost the weight for the role in Dallas Buyer's Club, but revealed but he made up for his lack of calories when filming finished.

'When I was done, I prepared the ultimate cheeseburger,' he said. 'It took me 45 minutes. The friend I was eating with had already finished by the time I had taken my first bite!'

The star, who will battle Leonardo DiCaprio and British hopeful Chiwetel Ejiofor for the Best Actor Oscar on March 2, said his extreme diet actually made him feel intellectually sharper.

'I'm trying to hang on to it as much as I can. I was hungry for knowledge,for information. There's a real benefit for being hungry, curious, interested," he said.

"I got up at 4am like clockwork. I like the silence of the world between 4 and 6am. Now I like to sleep a little past 4 for sure."

Luckily, his family including three children and wife Camila Alves helped him along the way.

"The hard part is making the decision to do it," he revealed.

"So when I know I need to lose the weight then it was easy. I had support from my family. I became a nice little hermit and I enjoyed it."

After several years in the rom-com wilderness, the actor is being recognised for his acting abilities winning the Best Actor award at the Globes and the Critics' Choice Awards.

"I have been having a lot of fun," he said. "More fun than I've ever been having. It's a privilege to do this. We don't do it for the results. I have great stories and experiences from Dallas Buyer's Club."